Crowning Music of Awesome: Like in Breath of Death VII, the battle themes are intense and keep your adrenaline pumping. Made even more awesome by the fact that you can get the entire OST for free at Zeboyd Games' website.
That One Boss: The Ape Princess has about 10 times more health than all the previous bosses combined, she hits absurdly hard, and her first move is always a spell that makes her mooks Nigh Invulnerable so long as she's still alive. Oh, and thanks to the battle system, she'll only get more powerful the longer the battle goes on. Have fun! She only starts doing insane damage, however, if you inflict the Insanity effect on her.
The Bonus Boss, if only because you need to do an absurd amount of damage in a very short amount of time. This is doable at 40+, but the boss is recruited once you beat him, and he's always at level 40. Going too high leaves him in the dust.